1. Field of the Invention
The present invention relates generally to projection lithographic methods and systems for producing integrated circuits and forming patterns with extremely small feature dimensions. The present invention relates particularly to extreme ultraviolet soft x-ray based lithography and radiation manipulating lithography elements which reflectively operate on and manipulate extreme ultraviolet soft x-ray radiation to illuminate, project, and reduce pattern images that are utilized to form circuit patterns. The present invention relates to lithography elements and their use for reflecting extreme ultraviolet soft x-ray photons to enable the use of extreme ultraviolet soft x-ray radiation for lithography that surpasses current optical lithography circuit feature dimension performance.
2. Technical Background
The use of extreme ultraviolet soft x-ray radiation provides benefits in terms of achieving smaller feature dimensions but due to the nature of the radiation, it presents difficulties in terms of manipulating and directing such wavelengths of radiation and has delayed the commercial manufacturing use of such radiation. Current optical lithography systems used in the manufacturing of integrated circuits have progressed towards shorter optical wavelengths of light, such as from 248 nm to 193 nm to 157 nm, but the commercial use and adoption of extreme ultraviolet soft x-rays has been hindered. Part of this slow progression to very short wavelengths of radiation such as in the 15 nm range, has been due to the lack of economically manufacturable mirror elements that can withstand the exposure to such radiation while maintaining a stable and high quality circuit pattern image. For the benefits of extreme ultraviolet soft x-rays to be utilized in the manufacturing of integrated circuits, there is a need for stable high quality glass lithography elements, that preferably allow for direct deposition of reflective coatings to the surface of the glass substrate body.
U.S. Pat. No. 5,956,192 describes a four mirror EUV projection system with lithography mirror elements including two convex mirror elements and two concave mirror elements. U.S. Pat. No. 5,353,322 describes a three mirror x-ray projection lens system with lithography mirror elements including a convex mirror and two concave mirrors. As noted from U.S. Pat. No. 5,698,113, current extreme ultraviolet soft x-ray lithographic systems are extremely expensive. U.S. Pat. No. 5,698,113 tries to address such high costs by trying to recover the surfaces of multilayer coated substrates by etching the multilayer reflective coatings from substrate surfaces of fused silica and ZERODUR type aluminosilicate crystalline glass-ceramics, even though such etching degrades the substrate surface. “Extreme Ultraviolet Lithography” by Richard Stulen and Donald Sweeney, Optics and Photonics News, August 1999, Vol. 10, No. 8, disclose an EUV reflective coating on a Si substrate (FIG. 3).
The present invention provides for economically manufactured lithography element substrates that are stable, ready and receptive to receiving multilayer reflective coatings and provide an improved extreme ultraviolet soft x-ray based projection lithography method/system. The present invention provides a stable high performance lithography element with the reflective multilayer coating directly deposited on the finished glass surface, and avoids costly and cumbersome intermediate layers between the glass substrate surface and the reflective multilayer coating.